This disclosure generally relates to refiners and refiner plates for refining lignocellulosic materials, such as fibers and other substances containing cellulose and lignin. This disclosure generally relates to the inlet of a refiner plate, including refiner plates designed for use in disc refiners, conical refiners, and conical-disk refiners.
In high consistency mechanical pulp refiners, lignocellulosic materials—such as wood fibers—are worked between two relatively rotating surfaces on which refiner plates are mounted. The plates typically have radial bars and grooves. The bars provide impacts or pressure pulses which separate and fibrillate the fibers, and the grooves enable feeding of the fibers between the refiner discs. Typically, each refiner plate has a radially inner inlet zone which is adapted for receiving wood chips, previously refined fiber, and/or other lignocellulosic material and at least one radially outer refining zone.
The inlet zone generally feeds the incoming lignocellulosic material into the refining zone and distributes the material around the refining zone. In many conventional refiners, the inlet zone of the refiner plates generally either feeds well or distributes well. In feeding and distributing the lignocellulosic material, the refiner plate's inlet zone may perform an initial refining operation on the cellulosic material to reduce the size of the material.
A conical-disk refiner, for example, may have good feeding ability in the first zone, occasionally referred to as the “flat zone,” as the centrifugal forces force the feed material along the gap created between two opposing refining plates. A second zone in a conical-disk refiner is the conical zone. In general, centrifugal forces normally project the feed material from the conical zone from the rotating element (which may be a smaller convex cone or plug) into the stationary element (which may be the larger concave element or shell). The feeding ability of the conical zone may not be as good as that of the flat zone. Accordingly, the conical zone may rely primarily on a forward flow of steam to promote forward movement of the pulp towards the refiner discharge which is typically located at the end of the conical zone or its larger diameter end.
A conical-disk refiner may generally lack significant mechanical centrifugal forces forcing the feed material from the discharge of the flat zone into the conical zone. Due to the absence of sufficient motive forces, the feed material may stall at the junction of the first and second zones. Stalling may potentially cause feed instabilities and other difficulties in operating the refiner, especially at higher production rates. In general, features on some conventional refiner plate designs may throw the fiber against the stator conical zone but may apply insufficient mechanical forces to feed forward the fiber along the gap between the conical zone rotor and stator.
An improved inlet section has been developed for refiners—such as conical, disk, and conical-disk refiners—and refiner plates for refining lignocellulosic material. In particular, an improved rotating element of a conical zone in a conical-disk refiner has been developed. The rotating element may improve feeding the lignocellulosic material forward from the junction of the flat and conical zones and may allow for a good distribution of the feed material around the rotating and stationary elements.